7. ABSTRACT Effective implementation of evidence-based practices (EBPs) to address complex and widespread public health issues, such as substance use disorders (SUDs) and HIV, remains a substantial challenge. Leadership and organizational context are associated with implementation climate and attitudes toward EBP, as well as clinical outcomes such as client satisfaction and quality of life. While there are many leadership development approaches, they are often not based on empirically supported approaches and curricula, nor are they specifically designed to develop strategic climates for EBP implementation. This project addresses these concerns and advances implementation science by testing the effects of the Leadership and Organizational Change for Implementation (LOCI) intervention. The goals of the LOCI intervention are to improve general leadership and implementation leadership and utilize organizational strategies to create a positive strategic organizational climate for EBP implementation. These should lead to more positive SUD treatment provider attitudes and behaviors that support EBP implementation outcomes of intervention fidelity and implementation process. Consistent with the Exploration, Preparation, Implementation, Sustainment (EPIS) conceptual framework, LOCI creates change at multiple levels within a provider organization (e.g., executives/mid- managers, workgroup leader, service provider) to foster a context supportive of EBP implementation and sustainment. Initial support for the feasibility, acceptability, and utility of the LOCI intervention have been successfully demonstrated in an NIH supported pilot study (R21MH082731, PI: Aarons). The proposed study will test whether LOCI can achieve change in outcomes of general and implementation leadership, implementation climate, implementation process, and EBP fidelity in SUD treatment agencies. Seventy-two workgroup leaders and their providers (i.e., subordinates) will be randomized to either the LOCI condition or a webinar control condition. All direct SUD treatment providers in both conditions will receive training in Motivational Interviewing (MI), a leading EBP for SUD and HIV prevention and treatment. The test of LOCI will occur within four agencies that provide SUD treatment and HIV services at multiple sites across California. The test of the LOCI intervention will include SUD service providers (n=432), workgroup leaders (n=72), and agency executives/mid-managers (n=16). Hypotheses will be tested comparing LOCI and control group outcomes of leadership, implementation climate, psychological safety climate, provider attitudes and behaviors, MI fidelity, and implementation process. We will also use mixed methods to explore cultural relevance, relative contribution of LOCI components, and differences between in-person and video training. The proposed study will provide a practical implementation strategy that can be utilized to improve workgroup leadership and strategic climate for EBP implementation.